The Gilnean Raven is a trainable pet in Mists of Pandaria. However, only Worgen are offered this option from Battle Pet Trainers. Once learned, all characters will have access to this pet. Worgen may also learn this pet from Audrey Burnhep in Stormwind.
NOTE: Once this pet is learned, it cannot be learned again from the trainer even if the pet is caged and sold.